Studies on palladium-catalyzed enantioselective cyclization of 3,4-allenylic hydrazines with organic halides

A convenient route to optically active pyrazolidine derivatives from Pd(0)/(R,R)-Bn-BOX-catalyzed enantioselective cyclization of 3,4-allenylic hydrazines in the presence of organic halides has been developed, the ee value is 75-84%. The absolute configuration of the products was determined by the conversion of one of the products to a known product prepared in this group. The reaction may proceed via the oxidative addition, intermolecular carbometallation of the allene moiety forming a π-allylic palladium intermediate, and the intramolecular enantioselective allylation.     

The 5-hexenyl cyclization

The cyclization of the 5-hexenyl radical to form the cyclopentylmethyl radical has been reexamined by kinetic EPR spectroscopy at temperatures between 183 and 232°K in cyclopropane solvent. The rate constant, k_c for this important radical rearrangement can be represented by where Θ = 2.3RT kcal/mol.     

Diene synthesis with 5-chloro-1-alkyl-2-pyridones

For the first time, we describe the diene synthesis of 5-chloro-1-alkyl-2-pyridones with N-phenylmaleic imide and have shown that the reaction proceeds nonstereoselectively with formation of a mixture of [4+2]cycloadducts with anendo andexo configuration. We have obtained 1,4-cycloadducts with 4-phenyl-1,2,4-triazoline-3,5-dione.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsklicheskikh Soedinenii, No. 5, pp. 687–691, May, 1997.     

Some cyclization reactions of ω-chloro-ω-acylamidoacetophenones

Substituted thiazoles, 1,4-benzothiazines, imidazo[2,1-b]thiazoles, and imidazo[1,2-a]pyridines containing acylamide residues as substituents were obtained by reaction of ω-chloro-ω-acylaminoacetophenones with thioamides, o-aminothiophenol, 2-aminothiazole, and 2-aminopyridine. Some of these substances can be used for the synthesis of heterocyclic bases with an unsubstituted amino group.     

Convergent synthesis of 2,3-bisarylpyrazolones through cyclization of bisacylated pyrazolidines and hydrazines

Cyclization of various bisacylated hydrazines and pyrazolidines using DBU or sodium hydride leads to the formation of various mono-, bi- and tricyclic pyrazolone scaffolds in 41-98% yield. The convergent nature by which the precyclization intermediates are constructed allows for rapid derivatization about the pyrazolone core.     

Structural, vibrational and quantum chemical investigations on 5-chloro-2-hydroxybenzamide and 5-chloro-2-hydroxybenzoic acid

The Fourier transform infrared (FTIR) and FT-Raman spectra of 5-chloro-2-hydroxybenzamide (5CBA) and 5-chloro-2-hydroxybenzoic acid (5C2HBA) have been recorded in the range 4000-400 and 4000-100 cm(-1), respectively. The complete vibrational fundamental modes of the compounds were assigned and analysed using the observed FTIR and FT-Raman data. The vibrational frequencies determined experimentally were compared with the theoretical wavenumbers calculated from ab initio HF and DFT-B3LYP gradient methods employing 6-31G** and 6-311++G** basis sets. The effect of halogen, hydroxyl groups and hydrogen bonding on the characteristic frequencies of the -COOH and -CONH2 group frequencies have been investigated. In 5CBA and 5C2HBA intramolecular hydrogen bond between a hydroxyl group and CO group makes a six membered ring, which causes the O?H interaction onto the resonance of the benzene ring. Comparison of the positions of the ν(OH) bands shows the ν(OH) band of 5CBA is located at considerably higher frequency which confirms a weaker hydrogen bond than in 5C2HBA.     

Intramolecular cyclization of dialkyl[2-(5-chloro-2-hydroxyphenyl)-2-phenylethenyl]phosphine oxides by the action of thionyl chloride

An efficient procedure has been proposed for the synthesis of quasiphosphonium salts, 2,2-dialkyl-6-chloro-4-phenyl-2H-1,2-benzoxaphosphinin-2-onium chlorides, via cyclization of dialkyl[2-(5-chloro-2-hydroxyphenyl)-2-phenylethenyl]phosphine oxides under the action of thionyl chloride.     

新显色剂5-氯-2-羟基重氮氨基偶氮苯的合成及其与镉(Ⅱ)的显色反应

合成了一种新型三氮烯类试剂5 氯 2 羟基重氮氨基偶氮苯,并对该试剂与镉(Ⅱ)的显色反应进行了研究。在pH10左右的硼砂 NaOH缓冲介质中,以TritonX 100为增溶增敏剂,该试剂与镉(Ⅱ)形成2∶1的红色络合物,其最大吸收波长位于524nm处,表观摩尔吸光系数ε为1.78×105L mol·cm,镉(Ⅱ)质量浓度在0～1 0μg mL范围内遵守比耳定律,已用于废水样品的测定。     

Reaction of 2-chloro-5-methylbenzoquinone with Β-aminocrotonic ester derivatives

The reaction of 2-chloro-5-methylbenzoquinone with -aminocrotonic ester derivatives was studied by PMR spectroscopy in CD₃COOD. The spectra indicate the formation of intermediate hydroquinone and quinone derivatives, which subsequently transform into the corresponding indoles. It was shown that the indolization proceeds unequivocally at the 3-position of the initial benzoquinone, and the rate of formation of the indole derivatives decreases with increase in the size of the substituent at the nitrogen atom of the -aminocrotonic ester. The starting, intermediate compounds and the end products observed in the PMR spectra were identified by comparison with specially synthesized compounds.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 324–328, March, 1990.     

Resolution of both enantiomers of 5-chloro-5-methyl-2-cyclopentenone

Reduction of (+/-)-5-chloro-5-methyl-2-cyclopentenone with BH(3).THF and catalytic (R)-2-methyl-CBS-oxazaborolidine gave readily separable diastereomers with high ee values. Oxidation of the diastereomers furnished the enantiomers of the chloromethylcyclopentenone.     

Reactions of diazo derivatives of 5-membered heterocycles with hydrazines

Interaction of hydrazine or dimethylhydrazine with 5-diazoimidazole-4-carboxamide produced, presumably via tetrazenes, high yields of 5-azidoimidazole-4-carboxamide. In contrast, when semicarbazide reacted with either the diazoimidazole or the analogous diazo-1,2,3-triazole, the yield of the azidoheterocycle was low, and the yield of biurea, and presumably the aminoheterocycle, was high. 3-Azidopyrazole-4-carboxamide was obtained from a reaction of hydrazine with the diazopyrazole. Both azido and amino derivatives were formed from reactions of diazo-imidazole esters with hydrazine or thiosemicarbazide.     

Comparison of amine-induced cyclization of 6-chloro-1-hexynylphosphonate and isobutyl 7-chlorohept-2-ynoate

The reaction of 6-chloro-1-hexynylphosphonate with primary and secondary amines afforded exclusively 2-aminocyclohexenylphosphonates in 62-85% isolated yields. In contrast, reaction of various amines with isobutyl 7-chlorohept-2-ynoate in acetonitrile at 70 °C gave (E)-sec-butyl 2-(1-alkylpiperidin-2-ylidene)acetates in 65-78% isolated yields. Calculations offer an explanation for the difference in the behavior of the two compounds classes. It is shown that C-C cyclization in the alkyne-phosphonate group occurs via an initial formation of a zwitterionic intermediate, which is stabilized by both an inductive effect of the phosphonate group and a newly formed hydrogen bond. The alkyne-carboxylate group, on the other hand, proceeds via enamine formation as a result of the smaller inductive effect of the carboxylate combined with involvement of an allene-like resonance form. This resonance form both delocalizes the negative charge in the zwitterionic intermediate making it to be less available for attack, and affects the geometry thus preventing formation of the stabilizing hydrogen bond. Hence, the zwitterionic intermediate of the alkyne-carboxylates is less stable leading to formation of an enamine, which is followed by N-C cyclization to give the azaheterocycles.     

The cyclization reaction of 5-hexenoyl chloride with tri-n-butyltin hydride

The title reaction under various conditions of solvent, temperature and concentration was found to give 1,5 cyclization product and the typical acyclic reduction products.